(1) Field of the Invention
The present invention pertains to beam mode discharge fluorescent lamps and more particularly to an arrangement for configuring the electrodes within a beam mode discharge fluorescent lamp.
(2) Description of the Prior Art
U.S. patent application Ser. No. 219,564, filed on Dec. 23, 1980, for a "Beam Mode Fluorescent Lamp", and assigned to the same assignee as the present invention, discloses a particular embodiment of a fluorescent lamp suitable for replacing the conventional incandescent bulb. Although incandescent lamps are inexpensive and convenient to use, they are considerably less efficient than fluorescent lamps.
In the above mentioned patent application, a single anode and cathode configuration is shown. This configuration requires three power terminals connecting the cathode and anode to two power sources. In an alternate configuration in this application, a four terminal and two power source configuration is shown in which a heating filament is provided to heat the cathode for the production of electrons.
It is desirable to minimize the number of power sources and connections from the power sources to the anode and cathode of the fluorescent lamp. Such a scheme provides for simpler assembly during manufacture and low end cost.
As pointed out in the above mentioned patent application, the placement and location of the anode and cathode is of critical importance.
One shortcoming of the above mentioned patent application is that, the excitatin of the fill material is incomplete. This situation results in a production of a lesser amount of visible light than otherwise could be produced by the same lamp. Lamp voltage is typically 20-30 volts and requires a base mounted transformer to operate from line voltage.
One of the chief impediments to lamp life and operating efficiency due to light imprisonment is the high operating temperature of the lamp. Another consideration is the variable loading of a single hot cathode.